crispyspa

Other than saving money, what is the benefit to a "right size" ESC? I mean could someone put a [link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXBRBA&P=ML]200a 50v Hydra Ice[/link] in a Traxxas spartan without harming anything?

Could I put [link=http://www.hobbypartz.com/96m606-bigfoot60-4030-400kv.html]THIS[/link] motor on it with 10 cells (40c) and be ok?

The reason I ask is because the ESC would be in a REALLY small space and I don't want any fires to start in the hull.



Thoughts on this ESC? http://www.hobbypartz.com/07e-c-seaking-180a.html

Goldenduff

My understanding is over sizing is heavier and more expensive. Larger (4cell lipo plus) lipos generally don't have a BEC so on top of weight another battery is necessaey.

crispyspa

Weight really isn't a large concern. The wires on the craft will be long, probably up to 24 inches. It is an air prop driven 3 point hydro.

Here is the boat I plan to run it on. That engine is a Super Tigre g2300 mk2

Goldenduff

Keep the battery to esc short. From ESC to motor should be the long wires. If it's a glow conversion you will already have  Rx battery in situ. If it's in  a small space, presumably sealed, it might be worth placing the ESC on a heat conductive bed (?copper sheet) with the copper sheet running through the hull to the exterior to help increase heat disipation. All the best

crispyspa

10-4 on the wires, I do have the rx battery and it will be air tight. I really like the cooling idea. I may turn it around and have fins sticking out the top of the hull.

With the combination of that motor, (maybe one a little [link=http://www.hobbypartz.com/96m607-bigfoot110-5325-295kv.html]bigger[/link]) one. [link=http://www.hobbypartz.com/77p-sl5000-5s1p-40c-5555.html]2 batteries[/link] and esc, will the ESC or the batteries heat up to the point of destruction?

Goldenduff

That lipo should be good. Do you know what prop that Motor requires? I think, but I could be wrong, that to get at the stated 2000w of power using a 290kv motor using a five cell you are going to need quite a large diameter prop, maybe even a relatively expensive 4 blader?

crispyspa

I was going to run 10 or 12 cells on that 290 KV motor....probably 10 cells I was thinking of a 16" two blade APC prop, maybe 16x10.
On the 400 kv I was thinking 10 cells and a 16x8 two blade APC

I'll have to shoot over to the airplane guys for suggestions on prop size.

Got RPM

There is no good solution for your ESC. Wires 24" long with high amp draw equals ESC failure. Given the relatively low rpm you will be turning, long motor wires might work but it will be easy for the ESC to lose back EMF signal and mess up the rpm of the motor. I run motor wires about 8" on my latest airboat and it "commutates" well at ~16,000 rpm, but three times that length? I doubt it.

I asked a Castle tech about this very topic (but with 18" of wire) and he said to use shorter motor wires and longer pack wires. He also stated to be sure to use at least 5,000 mF of added capacitors to the ESC. In your case I'd put the ESC in a box below the motor and run the motor wires to the packs up forward. A big cap board is a good idea. Water cooling is easy, use a sponson pickup right below the ESC box or a water pickup rudder.

I mounted my ESC right below the motor.

Goldenduff

I have been adviced to keep battery wires short and motor wires long if distance is needed....

crispyspa

OK, so "extra" wire is out of the question. By my measurements, I could get away with 12" motor wires and 12" of battery wires. Would that be too much?

That would allow the ESC to be hidden in the hull directly under the motor pylon and the batteries mid point in the hull.

What would happen if I doubled up the wire? Two wires for each motor wire?

NobodyFamous

just to add my $0.02 - If you need to run a longer wire, you can, without issue.  BUT you must have an appropriate size wire.  Heat is based on the resistance of the wire over length.  If you look at a 200amp fuse, it's got a pretty small wire, but only 1/4 long.

Got RPM

The problem is not "resistance" or heat, but impedance which will, among other things, hurt the motor's commutation. Using larger wire diameter, or doubling the wires, will not solve that issue. Since your rpm is relatively low (but you have a lot of poles) you may be able to get away with 12" motor wires. The power wire issue can be handled with additional capacitance. Remember that total wire length includes the wire coming out of the motor and the wire on the batteries.



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